Another DCR/quench/cam overlap triangle question

-
Actually, you do not have to have a closed chamber to get quench. It's just a lot easier to get quench with a closed chamber. There are quench dome pistons that are made specifically for open chamber heads, but you must measure and mill the piston head to get the quench right. This was the whole reason Chrysler made the early 340 positive deck height, to get some quench, although it wasn't "much". lol
 
middleagecrisis said:
Thank you guys for doing some legwork for me. I went to go Thank you guys for doing some legwork for me. I went to gofastmath.comfastmath.com and use their calculator instead of the Wallace calculator. I came up with 10.571 static compression ratio and 8.95 to one dynamic. This formula didn’t give me a cranking PSI, however, it would seem to be right on the ragged edge of pump gas. Since we seem to have landed in the basic area of where the static and dynamic compression ratio is, I’ll degree in the cam and see where it falls and report back. In theory, I should be able to retard the cam timing to lower the dynamic compression ratio, but I’ll see where the cam falls straight up and report back. Heading out of town so I probably won’t get to this until Monday. Thanks again for all the input!
Click to expand...
I'm getting similar numbers to PRH. I think you're entering something incorrectly. You should be seeing somewhere near 9.9SCR/8.0DCR/164psi.
 
middleagecrisis said:
No disrespect intended here, as I know you know what you’re talking about. So am I wrong to shoot for the ~.040 “quench”, or just say screw it and get as thick a head gasket as I can find to lower my compression? I don’t know of any readily available Chrysler small block heads (stock casting) that were closed chamber. My heads are Cc’d at 70 cc, as I stated in my previous post. Just trying to set this up as optimal as possible with what I have. If you could answer the above question regarding head gasket and give some thought on where my cam should be installed, for instance, straight up, advanced, or retarded, I would be grateful. Thank you.
Click to expand...
I'll try to explain as best as I can. Your chamber is recessed into the head, probably by .100 or so. That means if you piston was at zero deck, with a .040 gasket, your "quench distance" would be .140 which is not "quench" Also I'm curious about your flat top pistons you say have no valve reliefs. I believe your actual compression ratio is lower than you think
 
mopowers said:
I'm getting similar numbers to PRH. I think you're entering something incorrectly. You should be seeing somewhere near 9.9SCR/8.0DCR/164psi.
Click to expand...
I hope you’re right. I don’t have the ability to take a screenshot of what I’m entering, as I’m out of town right now. I’ll try to do that tomorrow when I get home. Thanks again for everyone’s input.
 
middleagecrisis said:
I hope you’re right. I don’t have the ability to take a screenshot of what I’m entering, as I’m out of town right now. I’ll try to do that tomorrow when I get home. Thanks again for everyone’s input.
Click to expand...
If your pistons true have zero valve reliefs, your SCR is 10.5 and DCR is 8.56 w/ 176 psi cranking. With zero quench and iron heads, you may have problems.
 
Always can run a thicker gasket if turns out to be a problem.
 
I was gonna agree with #31, and suggest #32, but it looks covered.
In my opinion, you probably have too small a cam for the compression you have with iron open chamber heads.
And since you have no valve reliefs, and no quench, I'd start shopping for some big fat thick head gaskets.
 
I’m going to go with…..it’s these……

From before TRW and Sealed Power had merged, when they each had their own part numbers:

53CB1BCA-A28B-4004-8984-07285B64DBC2.jpeg



72AA168F-0669-466E-9959-FA2A6384C4D4.jpeg


I can’t find any specs on these, but the “equivalent” TRW piston should be a L2386F, but those only have a CH of 1.591, so in an uncut block they’d be down the hole .090”+.
I built a 360 for my dad with a set of the TRW’s back in 1990, and it ended up at a little under 9:1.
 
Last edited:
Well, it appears I was right on the S/P 2380P being the equivalent of the TRW L2386F.

But, Maybe I’m totally wrong as to what pistons the OP actually has.

E2865CA9-34F7-4CDE-9320-1BFF6D52F3B0.png
 
middleagecrisis said:
Rather than hijack the quench thread, I figured I would start my own with my combination. Putting together a fresh 360 (.060) with .044 quench (.005 below deck/.039 compressed head gasket) and a calculated DCR of 9.85-1 with a dynamic cranking pressure of 211.31. This is an iron headed (ported 915 J), forged flat top combination, running an Oregon 1176 re-grind. I see ethanol free 90 octane with Torco additive in my future! I was looking at the MGI speedware camshaft calculator, and trying to figure out where I should install this cam. The MGI formula has a box for advance, but I’m not sure what’s supposed to go in there. My information from Oregon cam grinders list a 110 lobe separation a 106 Intake Center line and a 114 Exhaust Center line. Any inputs on how to degree the cam for optimum performance would be appreciated. This is a weekend warrior car with 4.11 gears and a 3200 converter.
Click to expand...


How do you have .044 quench with an open chamber head? The piston needs to be out of the block with an open chamber head.
 
remytherat said:
You need closed chambered heads for quench. The effect doesn’t work with open chambers.

The problem is that you used the @ 0.50 specs to calculate dynamic. You need the advertised spec, which I believe is 274 on a 106 centerline, giving 63 after BDC for closing.
Click to expand...


You can get quench with an open chamber head, you just have to know what you are doing.

We need to stop telling people this.
 
I have KB356 in my 414. The raised portion is supposed to "fill in" part of the open chamber to mimic a closed chamber.
 
Newbomb Turk said:
How do you have .044 quench with an open chamber head? The piston needs to be out of the block with an open chamber head.
Click to expand...
I don’t. If you go back and read through the thread, my interpretation of figuring out quench was wrong. Pointed out to me by a more knowledgeable member.
 
Last edited:
PRH said:
Well, it appears I was right on the S/P 2380P being the equivalent of the TRW L2386F.

But, Maybe I’m totally wrong as to what pistons the OP actually has.

View attachment 1716409584
Click to expand...
I have that piston without the center button, or whatever you want to call it. People need to go back and look through the whole thread. I had the deck milled .095. I have .005 clearance between the top of the piston and the deck.
 
middleagecrisis said:
I don’t. If you go back and read through the thread, my interpretation of figuring out quench was long. Pointed out to me by a more knowledgeable member.
Click to expand...


The good news is you’re far enough in the hole you shouldn’t have a detonation issue.

Also, you can get quench with an open chamber head. How to do it is in the Chrysler engine books.
 
So, I have an indirect question regarding this. Lets say you have a cam that says on the card it installs at 106 ICL. You wheel it, and lo and behold it's in correctly with the crank sprocket on the "0" keyway. Does the ground in advance have an effect on where TDC is in the overlap triangle?
 
Newbomb Turk said:
The good news is you’re far enough in the hole you shouldn’t have a detonation issue.

Also, you can get quench with an open chamber head. How to do it is in the Chrysler engine books.
Click to expand...
This should get you up to speed. Here is the info provided in this thread so far.

Looking at the OCG site, the advertised duration for the 1176 cam is 274/286.
So, for a 106 int c/l the intake closing point is 63abdc

230/236@.050. 490(Intake)/.493(exhaust), 1.5 rocker ratio, 110 lobe separation, 106 intake c/l.

4.060 bore, 3.58 stroke, 6.123” rod lenght

Heads were Cc’d at 70 by my machine shop.

As a refresher for those that don’t read the whole thread, the block was decked .095 and I have a true flat top with no valve reliefs and .005 piston to deck clearance.
 
middleagecrisis said:
I have that piston without the center button, or whatever you want to call it. People need to go back and look through the whole thread. I had the deck milled .095. I have .005 clearance between the top of the piston and the deck.
Click to expand...
My suggestion is, fairly early in the assembly process……. you should be degreeing in the cam and checking valve to piston clearance.
 
PRH said:
Compression ratio:

760 swept
70 chamber
9 gasket
5 valve pockets
1 top ring crevice
1 deck clearance
————
846 total
86 total minus swept
————
9.83cr(846/86)
Click to expand...
Adjusting the numbers to reflect no valve pockets…..
841/81 = 10.38:1
 

You must log in or register to reply here.
-

Similar threads

pntastar69
Started Another One - Revell Anglia
Replies
1
Views
179
1969cuda
1969cuda
9secRR
Another higher HP SB build
2
Replies
26
Views
836
9secRR
9secRR
robsimmons
Interest in another Group Buy: Wiseco "Big Bore" pistons up to 3.504"
Replies
8
Views
212
RustyRatRod
RustyRatRod
robsimmons
Interest in another Group Buy: Molnar 7" Connecting rods for CAST crank
Replies
8
Views
328
robsimmons
robsimmons
Oldmanmopar
Another loss of a nice car
2
Replies
31
Views
2K
nutz
nutz
Back
Top Bottom